Under physiological conditions, the nose functions to provide active warming and heating of breathing air. When a patient is undergoing artificial respiration however the nose is shunted by a flexible tube, whose end is inserted into the trachea. The moistening and warming action on the breathing gases, which is absolutely essential for normal function of the lungs, is presently performed by an apparatus, which more particularly operates in accordance with two principles. A first part of the apparatus actively imparts heat and moisture to the air. In this case for instance dry, cold air is caused to pass through an electrically heated water bath moistener and thereby conditioned prior to being supplied to the patient. A second part of the apparatus operates passively as a heat and moisture exchanger (H. M. E.). In this case heat and moisture are removed from the moist, warm expired air and are then imparted to the cold, dry air to be inspired without an additional active supply of heat and moisture from the surroundings taking place.
In accordance with this prior art it is admittedly possible for the apparatus to supply sufficiently tempered and moistened respiratory air when there is an active supply of heat and moisture, but however very involved technical and nursing measures are necessary so that production and running costs of such equipment are very high. In contradistinction to such apparatus, there are less complex, simply designed and simply operated passive heat and moisture exchangers, but they have not so far provided a sufficient moistening and warming action for artificial respiration.
In an earlier application, see European patent publication 0 413 127 A2, the applicant has described an apparatus for warming and moistening breathing air for artificial respiration of the type initially mentioned in the case of which the above mentioned advantages are obtained by a combination of independent passive heat and moisture exchangers with an active heat and moisture exchanger. However, this prior art device is relatively complex in design. Furthermore, such a device involved some problems owing to there being an excessive dead volume, which due to the re-inspiration of exhaled air had a particularly pronounced effect in the case of newly born babies, owing to their small vital capacity.